Dear French person, …

Thanks for writing. The “Jack” in the “Jack be nimble” rhyme refers to a fictional person named Jack. “Jacks” is a game played with little metal things (a “jack”) and a ball. It is described in detail at the top of this discussion.

A brief translation dictionary: “One-zees”, “two-zees”, etc., refers to the number of jacks you need to pick up. Non-standard English numbers like this is used in many street games. I don’t know if there’s a French equivalent (“trois-cize”?); it’s probably roughtly equivalent to “premiere, deuxieme, troisieme”, etc.